Isotonic dynamometry for the assessment of power and fatigue in the knee extensor muscles of females

Impairments in muscle power production and recovery following short-duratio n intense activity could lead to decreased performance and risk of injury. We developed a power test for the knee extensor muscles using torque-veloci ty testing and moderate isotonic loads. Twenty-eight female volunteers perf ormed three maximal efforts at each of four isotonic loads (27.1, 40.6, 54. 2 and 67.8 N . m). If the calculated regression line for the torque-velocit y data had an r(2) greater than or equal to 0.95 (i.e. an acceptable test), maximal power (408 +/- 56 W) was computed from the data. Immediately after torque-velocity testing, the subjects repeated maximal effort knee extensi ons with 33.9 N . m for three bouts of 15 repetitions with 15 s of rest to produce muscle fatigue, defined as a decrease in power output during isoton ic exercise. After a 4 min rest, the torque-velocity test was repeated and power calculated (345 +/- 48 W). For the group, the recovery of maximal pow er after the fatigue protocol was 85%. The extremes were represented by one subject who recovered only 70% of her maximal power and another who recove red completely (> 98%). Physiological differences in muscle power following repeated exercise could have an impact on the outcome of therapeutic inter ventions for sports injuries, fatigue syndromes and occupational over-use c onditions.